Furnace control



March 20, 1956 H|KEY 2,739,203

FURNACE CONTROL Filed March 8, 1952 29' f8 30 a a2 lNsuLm-iou 27 3 24/1 I I I) Z 7 11 f M F .1 F 2 W 34 W 1.34

2/ TO LDW VOLTAGE CONTROLS INVENTOR.

Leo RHic'fi-ey lwpggg A TTORNEYS United States Patent 3 Claims. (Cl. 200-138) Thelma M. Hickey, execudeceased, assignor to Thelma The invention relates tov controls for furnaces, and more particularly to a device for controllingthe operation of a gas furnace to automatically stop; operation of the furnace in the event the chimney fiuebecomes clogged so that products of combustion cannot pass upward through the same.

The usual gas furnace is; provided with a'plurality of low voltage controls, such as a low voltage thermostat, limit switch, Baso switch and. magneticv valve for controlling the admission of fuel. gas to the furnace burners.

It is also common practice in. gas furnaces to provide a sheet metal box, with open bottom, in the pipe leading from the combustion chamber of; the furnace. to the chimney.

in the event the chimney becomes. clogged as by an accumulation of soot, a broken flue liner, birds nests built in the chimney flue, orfrom other causes, so that the products of combustion fromthefurnace cannot pass up through the chimney, they are discharged through the open bottom of this box intotthe basemenhor other room in which the furnace is installed.

Since these products of combustion are usually heavily laden with carbon-monoxide, the lives and health of the occupants of the house are seriously endangered if the furnace is permittedto-continue operation under such conditions.

It is therefore anobjectof the present inventiont'o'provide controlmeansfor immediately stopping operation of a gas furnace in the event the chimney becomes clogged.

Another object is to provide such control means immediately breaking the circuit to the low voltage controls in the event the products of combustion cannot pass up the chimney.

A further object is to provide such control means including a bi-metal member located in an open bottom box in the chimney pipe, whereby when the flow of products of combustion to the chimney are interfered with the bi-metal member will be quickly heated thereby and will be operated to break the circuit to the low voltage controls of the furnace.

Another object is to provide means for holding said bimetal member in open position until it is manually reset to close the circuit.

The above objects together with others which will be apparent from the drawing and following description, or which may be later referred to, may be attained by constructing the improved furnace control in the manner hereinafter described in detail and illustrated in the accompanying drawing, in which;

Fig. 1 is a vertical, sectional view through a sheet metal box with open bottom, located in the chimney pipe between the furnace and the chimney, showing the bi-metal member located therein;

Fig. 2 a vertical, sectional view, taken as on the line 22, Fig. 1; and,

Fig. 3 a horizontal, sectional view, taken as on the line 33, Fig. 1.

Referring now more particularly to the embodiment ice 2v of the invention shown in the drawing, in which similar reference numerals refer to similar parts throughout, a sheet metal box 10 is shown, being open at its bottom as indicated at 11.

An inlet 12 is provided in one side wall of the box, communicating with the pipe 13 which'leads from the combustion chamber of the furnace, and an outlet 14 is provided in the top wall of the box, leading to the chimney.

Thus products of combustion from the furnace will enter the box through the inlet 12 and pass directly upward out of the box through the outlet 14 to the chimney, while the lower portion of the box is not contacted by the hot products of combustion and remains relatively cool.

it will be evident that in the event the chimney becomes clogged so as to interfere with the passage of these hot gases therethrough, they Will be discharged through the open bottom of the box, quickly raising the temperature thereof.

Located within the lower, normally cooler portion of the box is a thermostatic make-and-brcak device forming an important part of the invention. For this purpose an insulation block 16- is mounted in one side wall of the box, near the lower open end 11 thereof, and a spaced pair of binding posts 17 and 13. are mounted in said insulation block.

A wire 1? leads from the transformer 20 to the binding post 17, and. a wire 21. leads fromthe binding post 18 to the lowvoltage controls; The circuit to the low voltage controls is completed by. a wire 22 which leads fromthe transformer 2i) to the lowvoltage controls. The transformer may be connected to the power line as by the flexible cord 23, in usual and conventional manner.

A substantially hairpin. shaped, bi-metal bar 24 is provided at one end with thev angular terminal 25 clamped between the nuts 26 upon the post 17. The other, or longer, leg 27 of the bi-metal member has the angular contact. 28- thereon which normally en ages the angular contact 29 upon the post 18, thus closing the circuit from the transformer to the low voltage controls of the furnace.

A trigger lever 39- is' pivoted at oneend upon the post- 1 7' and insulated. therefrom as indicated at 31 in the normal, closed position of the bi-metal member 24-, the free end of the trigger lever 3-0 rests upon the top edge of the leg 27 of the bi-metal member, as best shown in Figs. 1 and 2.

A notch 32 is formed in the lower edge of the trigger lever 39 and adapted to engage the leg 27 of the bi-metal member when the same is operated to open position, as shown in broken lines in Fig. 3, so as to engage and hold the leg 27 in open position until the same is again manually reset.

For the purpose of easily resetting the trigger lever 30, a link 33 is pivotally connected thereto and hangs down through the open lower end of the box 10, and may be provided with a ring 34 at its lower end which may be easily grasped between the thumb and forefinger for raising the trigger lever 39 to permit the leg 27 of the bi-metal member to spring back to normal or closed position.

In the operation of the device the hot products of combustion from the furnace will pass from the pipe 13 to the inlet 12 of the box 10 and directly up through the outlet 14 of the box to the chimney pipe 15, thus not coming into contact with the bi--metal member 24 which remains relatively cool.

In the event the chimney becomes clogged, so as to interfere with passage of products of combustion of the furnace, these hot products of combustion, containing considerable carbon monoxide, will pass down over and around the bi-metal member 24, instantly heating the same so that the leg 27 thereof will expand, or spring out, to the broken line position shown in Fig. 3, breaking the contact at 28-29, thus immediately stopping the operation of all of the low voltage controls of the furnace so that the furnace is quickly cut off in order to prevent further discharge of carbon monoxide gas into the house.

As the leg 27 of the bi-metal member springsto the open position, the trigger lever 3% will drop down, the

notch 32 engaging the leg 27 and holding it in open position. When the furnace is thus shut off it gives warning to the householder who upon investigation will find that thebi-metal member has expanded, breaking the circuit.

The chimneyshould be repaired, so that gas may pass therethrough, after which the trigger lever 3% may be raised by pushing upward upon the ring 3 4, permitting the leg 27 of the bi-metal member to spring back to closed position, as shown in full lines in Fig. 3, and the furnace may again be operated normally.

From the above it will be obvious that a simple, inexpensive and efficient device is provided for immediately cutting off the furnace in the event of clogging of the chimney so as to immediately stop the discharge of poisonous carbon monoxide into the house.

In the foregoing description, certain terms have been used for brevity, clearness, and understanding, but no unnecessary limitations are to be implied therefrom beyond the requirements of the prior art, because such words are used for descriptive purposes herein and are intended to be broadly construed.

Moreover, the embodiments of the improved construction illustrated and described herein are by way of example, and the scope of the present invention is not limited to the exact details of construction.

Having now described the invention or discovery, the construction, the operation, and use of preferred embodiments thereof, the advantageous new and useful results obtained thereby; the new and useful constructions, and reasonable mechanical equivalents thereof obvious to those skilled in the art, are set forth in the appended claims.

I claim:

1. A thermostatic switch, an electrical circuit in which the switch is located, said switch comprising a horizontally disposed bimetal bar of substantially hairpin shape having one leg fixed to one side of the circuit, a contact point in the other side of the circuit, the other leg of said bimetal bar being normally in contact with disposed bimetal bar of substantially hairpin shape having one leg fixed to one side of the circuit, an outwardly disposed angular contact point in the other side of the circuit, the other leg of said bimetal bar having an inwardly disposed angular terminal normally in contact with said contact point, and an insulated trigger lever pivotally mounted at a point spaced from said other leg and having a notch in its free end portion, said trigger lever normally resting upon said other leg and being adapted to drop into position to engagethe notch with said other leg of the bimetal bar when it moves to open position to hold said other leg in open position.

3. A thermostatic switch, an electrical circuit in which the switch is located, said switch comprising a horizontally disposed bimetal bar of substantially hairpin shape having oneleg fixed to one side of the circuit, a contact point in the other side of the circuit, the other leg of said bimetal bar being normally in contact with said contact point, and an insulated trigger lever pivotally mounted at a point spaced from said other leg and having a notch inits free end portion, said trigger lever normally resting upon said other leg and being adapted to drop into position to engage the notch with said other leg of the bimetal bar when it moves to open position to hold said other leg in open position, and a link depending from the trigger lever for manually tripping said trigger lever to permit said other leg to move to closed position.

References Cited in the file of this patent UNITED STATES PATENTS 1,373,128 Freese Mar. 29, 1921 1,385,999 Howard Aug. 2, 1921 2,091,035 Foster Aug. 24, 1937 2,184,983 Tornquist Dec. 26, 1939 2,216,748 Lindemann Oct. 8, 1940 2,254,983 Tate Sept. 2, 1941 2,344,946 Landon Mar. 28, 1944 

